EP1435702A2 - Réseau en anneau autorégénérateur bidirectionnel à multiplexage en longueur d'onde - Google Patents

Réseau en anneau autorégénérateur bidirectionnel à multiplexage en longueur d'onde Download PDF

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Publication number
EP1435702A2
EP1435702A2 EP03027872A EP03027872A EP1435702A2 EP 1435702 A2 EP1435702 A2 EP 1435702A2 EP 03027872 A EP03027872 A EP 03027872A EP 03027872 A EP03027872 A EP 03027872A EP 1435702 A2 EP1435702 A2 EP 1435702A2
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EP
European Patent Office
Prior art keywords
optical
ring network
optical signals
wdm
outer rings
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03027872A
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German (de)
English (en)
Other versions
EP1435702A3 (fr
Inventor
Jong-Kwon Samsung Electronics Co. Ltd. Kim
Sang-Hyun Samsung Electronics Co. Ltd. Doh
Yun-Je Samsung Electronics Co. Ltd. Oh
Ki-Cheol Samsung Electronics Co. Ltd. Lee
Jong-Hun Samsung Electronics Co. Ltd. Lee
Hak-Phil Samsung Electronics Co. Ltd. Lee
Se-Kang Samsung Electronics Co. Ltd. Park
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Samsung Electronics Co Ltd
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Samsung Electronics Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Samsung Electronics Co Ltd filed Critical Samsung Electronics Co Ltd
Publication of EP1435702A2 publication Critical patent/EP1435702A2/fr
Publication of EP1435702A3 publication Critical patent/EP1435702A3/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/03—Arrangements for fault recovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0287—Protection in WDM systems
    • H04J14/0289—Optical multiplex section protection
    • H04J14/0291—Shared protection at the optical multiplex section (1:1, n:m)
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2581—Multimode transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/27—Arrangements for networking
    • H04B10/275—Ring-type networks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/021—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM]
    • H04J14/0212—Reconfigurable arrangements, e.g. reconfigurable optical add/drop multiplexers [ROADM] or tunable optical add/drop multiplexers [TOADM] using optical switches or wavelength selective switches [WSS]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0201—Add-and-drop multiplexing
    • H04J14/0202—Arrangements therefor
    • H04J14/0213—Groups of channels or wave bands arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J14/00—Optical multiplex systems
    • H04J14/02—Wavelength-division multiplex systems
    • H04J14/0278—WDM optical network architectures
    • H04J14/0283—WDM ring architectures

Definitions

  • the present invention relates to an optical network, more particularly to an optical network employing a WDM (wavelength-division-multiplexing) technique.
  • WDM wavelength-division-multiplexing
  • a WDM technique enables the transmission of a plurality of optical signals through a single strand of an optical fiber, it has become possible to transmit a plurality of very high-speed mass-storage optical signals. With the aid of a switch that add/drop the optical signal in the optical layer, it is possible to build an optical network based on the WDM technique.
  • a WDM optical network is generally classified into a ring network using an optical add/drop multiplexer and a mesh network using an optical cross-connect.
  • the WDM optical network transmits very high-speed mass-storage data through each optical fiber, thus requiring the WDM optical network to effectively cope with any undesirable failures in the system.
  • the mesh network nodes of each optical network are connected to each other through a plurality of optical fibers, so that a protection switching is carried out through a complicated procedure at a low-speed when the system fails.
  • the ring network only two or four strands of optical fibers are connected to the optical add/drop multiplexer, thereby enabling easier switching when the system fails. For this reason, the ring network is widely used in the market.
  • a node of a WDM ring network includes an optical add/drop multiplexer having a switching unit for adding/dropping an optical signal and a switching device for performing a protection switching of the network.
  • the WDM ring network is divided into a path protection switching network and a link protection switching network depending on the protection switching manner.
  • the WDM ring network uses two or four strands of optical fibers.
  • the WDM ring networks are classified into a unidirectional network and a bidirectional network depending on the transmission direction of data.
  • a conventional WDM ring network including two strands of optical fibers and bidirectionally transmitting the optical signal uses a link protection switching method utilizing a loop-back of the optical signals.
  • FIG 1A and 1B are respectively illustrates a construction and a protection switching according to a conventional bidirectional optical network using a link protection switching.
  • each node of a ring network includes optical add/drop multiplexers 10a to 40a and 10b to 40b for adding/dropping optical signals through inner and outer rings 2 and 4, and 2x2 switching devices 110 to 180 for executing a switching for the protection purposes.
  • the outer ring 4 transmits optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N
  • the inner ring 2 transmits optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N .
  • the outer ring 4 transmits the optical signals clockwise and the inner ring 2 transmits the optical signals counterclockwise.
  • the optical network transmits an optical signal to an opposite direction by looping-back the optical signal through two 2x2 switching devices, which are positioned at the both ends of the link with the error.
  • the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N intended to be transmitted to the optical add/drop multiplexer 20a from the optical add/drop multiplexer 10a are looped back to an optical add/drop multiplexer 10b through a switching device 120 and transmitted counterclockwise through the inner ring 2.
  • optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N transmitted through the inner ring 2 are transferred to the optical add/drop multiplexer 20a from an optical add/drop multiplexer 20b through a switching device 130, thereby completing the switching.
  • 2x2 switching devices 110 to 180 are maintained in a bar state, so that a signal applied to an input part i 1 is transferred to an output part o 1 , and a signal applied to an input part i 2 is transferred to an output part o 2 .
  • 2x2 switching devices 110 to 180 maintain in a cross state, so that a signal applied to the input part i 1 is transferred to the output part o 2 .
  • FIG 1B when a switching device 130 is positioned in the cross state, in addition to the optical signals passing through the link with the error, the optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , ....
  • ⁇ 2N which are transmitted in a counterclockwise direction from the optical add/drop multiplexer 20b to the optical add/drop multiplexer 10b, are looped back so that the optical signals are transmitted in a clockwise direction through the outer ring 4. Then, the optical signals are transferred to the optical add/drop multiplexer 10b from the optical add/drop multiplexer 10a through the switching device 120. Switching devices that are remote from the link having the fault are still maintained in the bar state.
  • FIG 2 shows a construction of a conventional optical cross-connect.
  • the optical signals transmitted through the upper multiplexers have wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N
  • the optical signals transmitted through the lower multiplexers have wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N .
  • multiplexing and demultiplexing operatons have to be carried out for an upper optical add/drop multiplexer 10a.
  • the capacity of a multiplexer 13 and a demultiplexer 12 has to be determined, by considering the loop-back of the transmitted optical signals in such a manner that the optical signals having wavelengths of ⁇ N+1, ⁇ N+2, ⁇ N+3, .... ⁇ 2N can pass through the upper optical add/drop multiplexer 10a.
  • the multiplexing and demultiplexing works have to be carried out for a lower optical add/drop multiplexer 10b to allow the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N to pass through the upper optical add/drop multiplexer 10a. Accordingly, the capacity of the multiplexer and the demultiplexer of the optical add/drop multiplexer for transferring N signals is determined as 1x2N.
  • optical signal passing through a normal link is looped back together with the optical signal passing through the link where the error occurred.
  • optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N and passing through the normal link in the inner ring 2 are looped back, so they are transmitted in a clockwise direction of the outer ring 4.
  • the transmitted optical signals are interrupted and suffers data loss.
  • the present invention provides an effective and economical bidirectional WDM, self-healing ring network capable of reducing the capacity of the multiplexer and demultiplexer of an optical add/drop multiplexer and transmitting optical signals without looping back the optical signals when not warranted.
  • a WDM filter is provided to the optical add/drop multiplexer, thus allowing the optical signals passing through the normal link without being looped back.
  • a bidirectional WDM self-healing ring network includes an outer ring network and an inner network for processing N units of optical signals and performing a protection switching by using the outer ring network when the inner ring network has a fault or vice versa.
  • the bidirectional WDM self-healing ring network includes: a node including; optical add/drop multiplexers positioned in the inner ring network and the outer ring network and having a demultiplexer and a multiplexer with a capacity of 1xN, respectively; a pair of switching devices extending through the outer ring network and the inner ring network and further positioned between the optical add/drop devices and an optical fiber link connected to other node; and, a plurality of WDM filters positioned at the both ends of the optical add/drop multiplexers and including a first port connected to the switching devices allowing all wavelength bands to pass therethrough; a second port only allowing optical signals having wavelength bands processed through one end of the ring networks to pass therethrough and connected to one end of the optical add/drop multiplexer provided in the ring network; and, a third port allowing optical signals having wavelength bands processed through the other ring network to pass therethrough and connected to the other end of the optical add/drop multiplexer, wherein, when the fault occurs in the optical fiber link,
  • a node in a bidirectional WDM ring network including an outer ring for processing N units of optical signals having a first wavelength band and an inner ring for processing N units of optical signals having a second wavelength band, the node comprising:
  • the switch device coupled to an optical link with the link failure transfers optical signals to one of the inner and outer rings without the link failure.
  • the switching devices is a 2x2 optical switch.
  • the ring network upon a detection of a link failure, is operative to transfer optical signals with the first and second wavelength bands to one of the inner and outer rings in a reverse direction.
  • the inner and outer rings is a bypass circuit using a loop-back operation when one of the inner and outer rings fails.
  • the outer rings transmits optical signals in a clockwise direction and the inner rings transmits the optical signals in a counterclockwise direction.
  • the switched optical signals are multiplexed and demultiplexed by the optical add/drop multiplexer.
  • the plurality of optical add/drop multiplexers comprises a multiplexer and a demultiplexer for processing optical signals received therein.
  • the switching devices is a 4x4 optical switch.
  • the ring network is operative to transfer optical signals traveling on an optical line having the link failure to one of the inner and outer rings in a reverse direction.
  • FIG 3 is a view showing an optical add/drop multiplexer and a 2x2 optical switching device according to a first embodiment of the present invention.
  • FIGS. 4A and 4B are views showing a ring network using the optical add/drop multiplexer and the 2x2 optical switching device according to the first embodiment of the present invention shown in FIG 3.
  • FIG 4A represents the ring network with a transmission link operating a normal mode
  • FIG 4B represents the ring network, in which an optical fiber transmission link connecting one optical add/drop multiplexer to another optical add/drop multiplexer has a failure.
  • each node of an outer ring network 4 and an inner ring network 2 includes optical add/drop multiplexers 210a and 210b for adding/dropping optical signals.
  • 2x2 optical switching devices 110 and 120 are positioned at both sides of the optical add/drop multiplexers 210a and 210b while connecting the outer ring network 4 to the inner ring network 2.
  • the outer ring network 4 provides a bypass circuit using a loop-back configuration when an optical fiber link of the inner ring network 2 has a failure. That is, the outer ring network 4 acts not only as a normal ring network, but 5 also as a protection switching network for the inner ring network 2.
  • the inner ring network 2 acts not only as a normal ring network, but also as a protection switching network for the outer ring network 4.
  • the outer ring network 4 transmits optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N and the inner ring network 2 transmits optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N .
  • the outer ring network 4 transmits the optical signals clockwise and the inner ring network 2 transmits the optical signals counterclockwise.
  • the optical add/drop multiplexers 210a included in each node of the outer ring network 4 adds or drops the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N , clockwise.
  • the optical add/drop multiplexers 210b included in each node of the inner ring network 2 adds or drops the optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N , counterclockwise.
  • WDM filters 310, 312, 314, and 316 are connected to both ends of the optical add/drop multiplexers 210a and 210b.
  • the WDM filters 310, 312, 314, and 316 multiplex or demultiplex signals having wavelength bands of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N and wavelength bands of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N .
  • the WDM filters 310, 312, 314, and 316 have a first port allowing signals to pass therethrough regardless of the wavelength bands thereof, a second port allowing signals having wavelength bands of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N to pass therethrough, and a third port allowing signals having wavelength bands of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N to pass therethrough.
  • At least one port of the WDM filters 310, 312, 314, and 316 is connected to the optical switching device 110 or 120, and at least one port of the WDM filters 310, 312, 314, and 316 is connected to another WDM filters 310, 312, 314, and 316 corresponding to the nodes of the ring network 2 or 4.
  • at least one port of the WDM filters 310, 312, 314, and 316 is connected to the optical add/drop multiplexer 210a or 210b.
  • the first port of the WDM filter 310 connected to the optical switching device 110 the second port thereof is connected to one end of the optical add/drop multiplexer 210a, and the third port of the WDM filter 310 is connected to the other end of the optical add/drop multiplexer 210a.
  • Each of the optical add/drop multiplexers 210a and 210b has a 1xN WDM demultiplexer 212, a 1xN WDM multiplexer 214, and N number of 2x2 optical switches 216-1, 216-2....216-N.
  • the capacity of the demultiplexer and multiplexer is set to 1xN, respectively, which is less than half of that of the conventional demultiplexer and multiplexer, which requires a capacity of (1x2N).
  • This can be achieved by incorporating a plurality of WDM filters for channeling signals according to predetermined criteria (explained later) during a link failure.
  • optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N are inputted into the optical add/drop multiplexer 210a of the outer ring network 4, and optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N are inputted into the optical add/drop multiplexer 210b of the inner ring network 2.
  • the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N inputted into the optical add/drop multiplexer 210a firstly pass through the optical switching device 110.
  • the 2x2 optical switching device when the ring network is normally operated, the 2x2 optical switching device is maintained in a bar state, so the signals applied to a first input part i 1 are transferred to a first output part o 1 , and the signals applied to a second input part i 2 are transferred to a second output part o 2 .
  • the optical switching device 110 since the optical switching device 110 is also maintained in the bar state, the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N applied to the first input part i 1 are transferred to the first output part o 1 , and outputted through the WDM filter 310.
  • the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N have been inputted into the first port of the WDM filter 310 through the optical switching device 110, the optical signals are transferred to the optical add/drop multiplexer 210a by passing through the second port, which allows the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N to pass therethrough.
  • the optical add/drop multiplexer 210a only receives the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N since an input terminal of the WDM filter 310 is connected to the second port.
  • the optical signals outputted from the optical add/drop multiplexer 210a are inputted into the second port of the WDM filter 312 connected to an output terminal of the optical add/drop multiplexer 210a.
  • the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N inputted into the second port are transferred to the optical switching device 120 through the first port and forwarded to the adjacent optical switching device 130.
  • the optical switching devices 120 and 130 positioned at both ends of the link are maintained in a cross state in response to a predetermined control signal.
  • the optical signals transferred to the first input i 1 of the optical switching device 120 are outputted through the second output o 2 of the optical switching device 120 and looped back to the first port of the WDM filter 316 connected to the second output o 2 of the optical switching device 120.
  • optical add/drop multiplexers of the present invention only multiplex or demultiplex optical signals, which are required to be added or dropped by the optical add/drop multiplexers. That is, the optical add/drop multiplexer 210b only processes the optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N .
  • ⁇ N are demultiplexed through the second port of the WDM filter 314 and multiplexed through the first port of the WDM filter 314, so that the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N are transmitted into an adjacent node together with the optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N .
  • Nodes that are remote from the failure link allow the optical switching devices to be maintained in the bar state, which is similar to the normal operation.
  • signals can be redirected to the correct destination node, via the number of WDM filters, with less dependence on the number of multiplexer and demultiplexer as in the prior art.
  • the looped-back optical signals are connected to each other via the WDM filters, thus allowing the capacity of the multiplexer and demultiplexer of the inventive optical add/drop multiplexer to 1xN.
  • FIG 5 illustrates an optical add/drop multiplexer and a 4x4 optical switching device according to a second embodiment of the present invention.
  • FIGS. 6A and 6B shows a bidirectional ring network using the optical add/drop multiplexer and the 4x4 optical switching device according to the second embodiment of the present invention shown in FIG 5. More specifically, FIG 6A represents the bidirectional ring network during a normal operation, and FIG 6B represents the bidirectional ring network, in which an optical fiber transmission link failure connecting an optical add/drop multiplexer to another optical add/drop multiplexer occurs.
  • optical add/drop multiplexers 210a and 210b and 4x4 optical switching devices 410 to 480 are connected to each other via WDM filters 310, 312, 314, and 316, and similar to the first embodiment.
  • the 4x4 optical switching devices 410 to 480 according to the second embodiment enables to switch the looped-back signals independently.
  • optical signals passing through the link failure are looped back together by means of the 2x2 optical switching devices 210 to 280.
  • optical signals passing though the link failure are looped-back only by means of the 4x4 optical switching devices 410 to 480.
  • two input/output terminals are added to the 4x4 optical switching devices 410 to 480 so as to connect only the looped-back signals through the WDM filters when a linkfailure occurs.
  • a third input part i 3a is connected to a third output part o 3a and a fourth input part i 4a is connected to a fourth output part o 4a .
  • the 4x4 optical switching devices 410 to 480 are provided with separate input/output terminals for looping back the optical signal having wavelength bands processed in one ring network and separate input/output terminals for transferring optical signals having wavelength bands processed in the other ring network when a link failure occurs in an optical fiber link of the ring networks, as explained in detail hereinafter
  • optical signals with the wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N applied to an input part i 1a are transferred to an output part o 1a , and then transferred to a WDM filter 310 connected the output port o 1a .
  • the WDM filter 310 demultiplexes the optical signals with the wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N and received via the second port thereof.
  • ⁇ N and have passed through the WDM 310 are demultiplexed by the 1 ⁇ N demultiplexer 212 of the optical add/drop multiplexer 210a, so that the optical signals can be added or dropped at this juncture.
  • the optical signals with the wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N are multiplexed by the 1xN multiplexer 214 and outputted through a WDM filter 312.
  • the optical signals with the wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N and outputted from the WDM filter 312 are transferred to an output part o 1b via an input part i 1b of the 4x4 optical switching device 420, and then transmitted to an adjacent node.
  • the WDM filter 316 demultiplexes the optical signals with the wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N using the third port thereof.
  • the optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N which have passed through the WDM 316, are demultiplexed through the 1xN demultiplexer of the optical add/drop multiplexer 210b, so that the optical signals are added or dropped at this juncture. Then, the optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , ....
  • ⁇ 2N are multiplexed through the 1xN multiplexer and outputted through a WDM filter 314. Thereafter, the optical signals having wavelengths of ⁇ N+1 , ⁇ N+2 , ⁇ N+3 , .... ⁇ 2N passing through the WDM filter 314 are transferred to an output part o 2a through an input part i 2a of the 4x4 optical switching device 420, and then transmitted to an adjacent node.
  • an optical fiber link failure occurs, for example, if the optical fiber link positioned between the optical switching device 420 and the optical switching device 430 of the outer ring network 4 experiences a link failure, the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N inputted into the optical add/drop multiplexer 210a of the outer ring network 4 cannot be forwarded to the optical switching device 430 through the optical switching device 420. Since the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N cannot be transmitted to the optical switching device 430, the optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , ....
  • ⁇ N are transmitted in clockwise direction by looping back the optical signals, while changing a switch state of the 4x4 optical switching device 420. Since the optical add/drop multiplexers 240b and 230b are positioned remotely away from the link failure point, the switch state of the switching device thereof is maintained is the same. As such, the looped-back optical signals are connected through the WDM filters, and signals are transferred without performing multiplexing or demultiplexing process. Ultimately, as shown in FIG 6B, the 4x4 optical switching device 430 positioned at the other end of the link allows the looped-back optical signals having wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N to be transferred to the optical add/drop multiplexer 220a.
  • FIGs. 7A to 7C are provided to illustrate the operation steps shown in FIG 6 in the event there is a link failure. Accordingly, FIGS. 7A to 7C shows the node state of a bidirectional ring network for a recovery switching according to the second embodiment of the present invention.
  • FIG 7A represents the node positioned at the left side of the link failure, in which the optical signals with the wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N to be transmitted in a clockwise direction are unable to transmit due to the link failure.
  • the optical signals are looped-back from an input part i 1b to an output part o 4b (shown as a solid line).
  • the optical signals are transmitted in a counterclockwise direction without being looped-back (shown as a dotted line).
  • the looped-back optical signals are multiplexed together with the optical signals transmitted in a counterclockwise direction through the WDM filters, so that the looped-back optical signals are transmitted to a counterclockwise adjacent node. Note that a slender solid line shown in FIG 7A indicates that optical signals are not transferred.
  • FIG 7B represents the node that is remote located away from the link failure, in which the looped-back optical signals and the optical signals, not affected by the link failure are transmitted to an adjacent node using the WDM filters.
  • FIG 7C represents the node positioned at the right side of the link failure.
  • the optical signals with the wavelengths of ⁇ 1 , ⁇ 2 , ⁇ 3 , .... ⁇ N which are looped-back in a counterclockwise direction, have to be transmitted clockwise, so the direction of the optical signals is switched to an initial state thereof using the optical switching device.
  • the input part i 4a is connected to the output part o 1a (shown as a solid line).
  • the optical signals, which are not affected by the link failure are transmitted without being looped-back (shown as a dotted line).
  • the bidirectional self-healing ring network of the present invention optical signals passing through a normal link is transmitted without being looped-back with the aid of WDM filters, regardless the occurrences of a link failure during recovery operation.
  • the capacity of the multiplexer and demultiplexer is reduced as much as a half when compared with the required capacity according to a conventional optical add/drop multiplexer.
  • the ring network according to the teachings of the present invention can be established at a low cost and further assist in better management of link failures.
EP03027872A 2003-01-03 2003-12-04 Réseau en anneau autorégénérateur bidirectionnel à multiplexage en longueur d'onde Withdrawn EP1435702A3 (fr)

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KR2003000357 2003-01-03
KR10-2003-0000357A KR100487215B1 (ko) 2003-01-03 2003-01-03 파장분할다중방식 자기치유 환형 광통신망

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EP1435702A2 true EP1435702A2 (fr) 2004-07-07
EP1435702A3 EP1435702A3 (fr) 2006-11-02

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US (1) US7133609B2 (fr)
EP (1) EP1435702A3 (fr)
JP (1) JP3908225B2 (fr)
KR (1) KR100487215B1 (fr)
CN (1) CN1516382A (fr)

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CN100367729C (zh) * 2004-09-28 2008-02-06 中兴通讯股份有限公司 一种光传输环网快速保护方法
US20150034169A1 (en) * 2013-08-02 2015-02-05 Goodrich Corporation Heated Inflation System

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CN1516382A (zh) 2004-07-28
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US7133609B2 (en) 2006-11-07
JP2004215272A (ja) 2004-07-29

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